GHSA-8fq9-273g-6mrg: Avo: Missing Authorization in Avo Association Attach Endpoint Allows Unauthorized Relationship Manipulation and Privilege Escalation

Summary A critical missing authorization flaw exists in Avo's association attach workflow. The UI and GET /resources/:resource/:id/:related/new path can check attach_<association>?, but the actual write endpoint, POST /resources/:resource/:id/:related, does not run the same authorization check before mutating the association. As a result, an authenticated low-privileged Avo user can bypass hidden/disabled attach controls and directly attach related records to a parent record by sending a crafted POST request. In applications where associations represent teams, tenants, roles, projects, users, memberships, ownership, or other authorization-bearing relationships, this can lead to privilege escalation and cross-tenant data exposure. Details The association attach route writes relationships through Avo::AssociationsController#create: config/routes.rb post "/:resource_name/:id/:related_name", to: "associations#create", as: "associations_create" The controller registers an attach authorization callback only for new, not for create: app/controllers/avo/associations_controller.rb before_action :set_attachment_record, only: [:create, :destroy] before_action :authorize_index_action, only: :index before_action :authorize_attach_action, only: :new before_action :authorize_detach_action, only: :destroy The new action is only the form-rendering step. The actual mutation happens in create: def create if create_association create_success_action else create_fail_action end end create_association then attaches the attacker-supplied related record to the parent: def create_association association_name = BaseResource.valid_association_name(@record, association_from_params) perform_action_and_record_errors do if through_reflection? && additional_params.present? new_join_record.save elsif has_many_reflection? || through_reflection? @record.send(association_name) << @attachment_record else @record.send(:"#{association_name}=", @attachment_record) @record.save! end end end The